Receive previous UDP packet even after relaunch

Receive previous UDP packet even after relaunch

[Jiading Guo]

Hi all,

I'm trying to run the Flow Filtering application[1] with DPDK 23.11.1
on Ubuntu 20.04 with Intel i210 NIC. Since i210 doesn't support IPv4
filtering, I removed the related code and made it print all received
packets as a simple receiver.

Then I noticed:
- launch this receiver program on one machine
- on another machine (connected back-to-back), a program sends UDP
packets in a while loop
- wait for several seconds, SIGINT the sender, then SIGINT receiver later
- relaunch the receiver, the program print several previous UDP
packets, even I'm not running the sender now

I'm new to DPDK but I guess that I'm quitting receiver first, so when
the NIC keeps receiving the packets and "marks" it ready, it has no
chance for `rte_eth_rx_burst` when doing the exciting routine after
SIGINT. However I'm expecting that after `rte_eth_dev_stop/close`, the
previously marked packets should be cleared. What could go wrong here?
Or should I clear it manually after launching?

I tried igb_uio and vfio-pci, but with no luck. I'm using `iommu=off`.

Best regards,
Jiading Guo

[1] https://doc.dpdk.org/guides-23.11/sample_app_ug/flow_filtering.html